C-H activation at the 3-position of pentane chains to form [N-C(sp3)-N]- complexes incorporating six-membered pallada(II)cyclic rings and pyridine, pyrazole and N-methylimidazole donor groups. Structural studies and comparison with [

Article abstract of DOI:10.1016/S0022-328X(00)00338-7

Alkylpalladium complexes bearing the [N-C(sp³)-N]^- donor motif and two six-membered palladacycles are generated on activation of C(sp³)-H bonds by palladium(II) acetate. Cyclopalladation of the new reagents 1,5-bis(pyridin

Full text of DOI:10.1016/S0022-328X(00)00338-7

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 607 (2000) 194–202
CꢀH activation at the 3-position of pentane chains to form
[NꢀC(sp3)ꢀN]− complexes incorporating six-membered
pallada(II)cyclic rings and pyridine, pyrazole and
N-methylimidazole donor groups. Structural studies and
comparison with [NꢀC(sp2)ꢀN]− complexes
Allan J. Canty a,*, Jim Patel a, Brian W. Skelton b, Allan H. White b
a School of Chemistry, Uni6ersity of Tasmania, Hobart, Tas., Australia 7001
b Department of Chemistry, Uni6ersity of Western Australia, Nedlands, WA, Australia 6907
Received 19 April 2000; accepted 21 May 2000
Dedicated to Professor Martin Bennett on the occasion of his retirement.
Abstract
Alkylpalladium complexes bearing the [NꢀC(sp3)ꢀN]− donor motif and two six-membered palladacycles are generated on
activation of C(sp3)ꢀH bonds by palladium(II) acetate. Cyclopalladation of the new reagents 1,5-bis(pyridin-2-yl)pentane
[CH2(CH2CH2py)2] (1), 1,5-bis(pyrazol-1-yl)pentane [CH2(CH2CH2pz)2] (2) and 1,5-bis(N-methylimidazol-2-yl)pentane
[CH2(CH2CH2mim)2] (3), followed by reaction with lithium chloride afford the palladium(II) complexes Pd{CH(CH2CH2py)2-
N,C,N%}Cl (5), Pd{CH(CH2CH2pz)2-N,C,N%}Cl (6) and Pd{CH(CH2CH2mim)2-N,C,N%}Cl (7), respectively. Abstraction of
chloride from 6 with AgBF4 in acetone generates the cationic acetone complex [Pd{CH(CH2CH2pz)2-N,C,N%}(OCMe2)][BF4] (8).
X-ray crystal structures of 5, 6 and 8 reveal tridentate [NꢀC(sp3)ꢀN%]− intramolecular coordination of the ligands. These structures
are compared with that of a closely related [NꢀC(sp2)ꢀN]− system in [Pd{2,6-(pzCH2)2C6H3-N,C,N%}(OH2)][BF4] (10), obtained
on cyclopalladation of 1,3-bis(pyrazol-1-ylmethyl)benzene followed by derivatisation to form the aqua complex. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Organopalladium; Intramolecular coordination; Cyclometallation; Crystal structure
[EꢀC(sp3)ꢀE]− system (III) [4], and for aryl systems
1. Introduction
[EꢀC(sp2)ꢀE]− this ring size is also rare (IV and V)
[5–8]. Complexes I–V have been synthesised via cyclo-
palladation reactions. We report here an investigation
of the applicability of the cyclopalladation strategy for
the synthesis of relatives of II containing six-membered
Intramolecular coordination systems with the sym-
metrical donor motif [EꢀCꢀE]− (E=donor element)
coordinated to palladium(II) have attracted consider-
able interest, but there are few examples where the
chelate rings using the reagents CH2(CH2CH2X)2 [X=
central carbon atom is an aliphatic sp3 centre (I–III)
pyridin-2-yl (py), pyrazol-1-yl (pz) and N-methylimida-
[1–4]. Only one of these is
a
six-membered
zol-2-yl (mim)], resulting in the synthesis of
[NꢀC(sp3)ꢀN]− systems of type VI. The new systems
contain nitrogen donor groups with different donor
abilities (mim\py\pz) [9], but providing similar co-
ordination geometries for the [EꢀC(sp3)ꢀE]− unit.
* Corresponding author. Fax: +61-3-6226-2858.
E-mail address: allan.canty@utas.edu.au (A.J. Canty).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00338-7

A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
195
Scheme 1.
2. Results and discussion
long reaction times (ꢀ12 h), and after this time the
major by-products detected were found to be the free
ligand and palladium(0). Isolation of the complexes in
low yield could result from several factors, including
palladation of other sites in the ligand followed by
decomposition. Thus, when 1,5-bis(pyrazol-1-yl)pentane
(2) and one equivalent of palladium acetate were refluxed
in acetic acid-d4 for 12 h, 1H-NMR analysis of the
product indicated deuterium incorporation into the 3, 4
and 5 positions of the pyrazole rings while no deuterium
incorporation into the alkyl chain was observed. When
1,5-bis(pyrazol-1-yl)pentane was treated under the same
conditions in the absence of palladium acetate no deu-
terium incorporation was observed. However, for 1,5-
bis(pyridin-2-yl)pentane (1) deuterium was incorporated
at one methylene group, (pyCHDCH2)CH2, and no
incorporation occurred in the absence of palladium
acetate. Insoluble decomposition products formed in an
analogous experiment for 1,5-bis(N-methylimidazol-2-
yl)pentane (3), and in the absence of palladium acetate no
deuterium incorporation was detected.
2.1. Synthesis and characterisation of complexes
The compounds CH2(CH2CH2X)2 (X=py, pz, mim)
were obtained on reaction of dibromoalkanes with alkali
metal reagents. Thus, 1,5-bis(pyridin-2-yl)pentane (1)
was prepared by treating a solution of 2-picolyllithium
with half an equivalent of 1,3-dibromopropane, follow-
ing a procedure used by Brzezinski and Zundel for the
synthesis of other bis(pyridin-2-yl)alkanes [10]. The pyra-
zole analogue, 1,5-bis(pyrazol-1-yl)pentane (2), was gen-
erated on refluxing a mixture of pyrazol-1-ylpotassium
and half an equivalent of 1,5-dibromopentane in tetrahy-
drofuran. Similarly, 1,5-bis(N-methylimidazol-2-yl)-
pentane (3) formed on addition of N-methylimidazol-2-
yllithium to half an equivalent of 1,5-dibromopentane.
Cyclometallated complexes 5–7 were found to be
generated on reaction of 1–3 with one equivalent of
palladium acetate in refluxing acetic acid, and isolated as
chloro complexes after reaction with lithium chloride
(Scheme 1). The best yields (12–35%) were obtained after
Fig. 1. Alkyl region of the 1H-NMR spectrum for Pd{CH(CH2CH2pz)2-N,C,N%}Cl (6).

196
A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
Table 1
Specific crystallographic details for Pd{CH(CH2CH2py)2-N,C,N%}Cl (5), Pd{CH(CH2CH2pz)2-N,C,N%}Cl (6), [Pd{CH(CH2CH2pz)2-
N,C,N%}(OCMe2)][BF4] (8), and [Pd{2,6-(pzCH2)2C6H3-N,C,N%}(OH2)][BF4] (10)
Complex
5
6
8
10
Formula
Crystal system
Space group
C15H16ClN2Pd
Monoclinic
P21/n (no. 14)
11.447(3)
8.825(2)
14.219(8)
96.57(3)
1427
C11H15ClN4Pd
Monoclinic
P21/a (no. 14)
17.166(4)
8.744(3)
8.486(3)
90.32(2)
1274
C14H20BF4N4OPd
Monoclinic
P21/c (no. 14)
9.152(2)
24.53(1)
8.188(5)
101.20(3)
1803
C14H15BF4N4OPd
Monoclinic
P21/c (no. 14)
7.859(1)
14.441(4)
14.895(5)
99.51(2)
1667
,
a (A)
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
4
4
4
4
Mr
366.2
1.704
14.7
732
345.1
1.800
16.5
688
453.6
1.670
10.8
908
448.5
1.782
11.6
888
Dcalc (g cm−3
)
vMo (cm−1
F(000)
)
Specimen (mm)
2qmax (°)
0.28×0.35×0.80
55
0.28×0.28×0.10
55
0.50×0.14×0.45
50
0.75×0.18×0.14
56
A*
nv
1.18, 1.62
174
1.7
3274, 2279
0.050, 0.062
1.16, 1.55
174
1.6
3694, 2552
0.049, 0.058
1.16, 1.57
244
1.0
3157, 1915
0.057, 0.066
1.19, 1.25
240
0.5
4017, 3062
0.037, 0.039
min, max
−3
,
ꢀDzmaxꢀ (e A
)
N, N0
R, Rw
(pzCH2)2C6H-N,C,N%}Cl (V: R1=R3=H, R2=Me)
[6], the fused six-membered palladacycles each exist in a
boat conformation and invert rapidly at room tempera-
ture. This results in a single CH2 resonance in the
1H-NMR spectrum, which splits into two resonances
on cooling as the inversion process slows. In complex 6,
although a similar inversion process occurs, the two sets
of protons Hc and Hc% each resonate at a different
frequency due to the lack of C2 symmetry within the
molecule.
In order to allow a comparison of structural data for
the [NꢀC(sp3)ꢀN]− systems in 5, 6 and 8 (see below)
with a [NꢀC(sp2)ꢀN]− system, the complex Pd{2,6-
(pzCH2)2C6H3-N,C,N%}Cl (9) was synthesised from the
reported complex [Pd{2,6-(pzCH2)2C6H3-N,C,N%}-
(O2CMe) [5]. However, this complex was not suffi-
ciently crystalline for structural analysis, and was sub-
sequently converted to the crystalline aqua derivative
[Pd{2,6-(pzCH2)2C6H3-N,C,N%}(OH2)}][BF4] (10). Al-
though the chloro complex may be readily obtained
from the acetato complex following procedures devel-
oped for 5–7, we report here an alternative synthesis
via the isolation of PdCl2{1,3-(pzCH2)2C6H4}, followed
by heating of this complex to form 10. Thermogravi-
metric analysis of the latter process indicates a weight
loss of 10%, close to that calculated for loss of HCl
(8.8%).
The complexes 5, 6 and 7 were characterised by
microanalysis and 1H-,13C-, COSY and HETCOR
1
NMR spectroscopy. A single set of H- and 13C-NMR
resonances for the N-heterocyclic donor groups for
each complex indicated the equivalence of the trans
donor groups. The methine proton resonances (2.2–2.6
ppm) occur at similar chemical shifts to the methine
resonance observed for the methylpalladium(II) com-
plex containing the [PꢀC(sp3)ꢀP]− system in I (2.22
ppm) [2]. The methine resonance for each complex
appears as a triplet of triplets due to coupling with the
two pairs of protons Hb and Hb% (Fig. 1). For com-
3
plexes 5 and 6 the J coupling constants could not be
determined due to overlapping resonances, however
values of 3.0 and 10.5 Hz were determined for 7.
The resonances for the two pairs of methylene pro-
tons Hc and Hc% each appear as a doublet of doublets of
doublets. The resonances were best resolved for com-
3
plex 6 (Fig. 1) for which one pair exhibits J=3.2, 8.2
2
3
Hz and J=13.2 Hz, and the other pair J=3.6, 8.0
2
Hz and J=13.4 Hz. The similarity between the cou-
pling constants for Hc and Hc% suggest that a rapid
inversion process occurs, since significant differences
3
between the J coupling constants for each pair would
be expected in a rigid system due to different dihedral
angles. The inversion process is still evident at low
1
temperature with no apparent change in the H-NMR
spectra for 6 between −50 and 50°C. As a result of
this inversion, through space interactions are inherently
difficult to interpret, so that methylene resonances can
only be assigned as either Hb or Hb%, or Hc or Hc% (Fig.
1). In the structurally related complex, Pd{3,5-Me2-2,6-
2.2. X-ray structural studies
To date there are no examples of X-ray crystal
structures of cyclopalladated, anionic [NꢀC(sp3)ꢀN]−

A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
197
units. Thus, X-ray crystal structures were determined
for complexes 5, 6, 8 (a derivative of 6 in an attempt to
obtain a structure for the [pzꢀC(sp3)ꢀpz]− kernel free of
disorder). Crystals of 5 and 6 suitable for single crystal
X-ray structure determinations were grown from
dichloromethane–petroleum ether (b.p. 60–80°C) and
chloroform–petroleum ether (b.p. 60–80°C) solutions,
respectively; crystals of 10 were obtained on diffusion
of diethyl ether into a solution of the complex in
acetone. Pertinent results of structure determinations
are quoted in Tables 1 and 2 and Figs. 1 and 2, the
remainder being deposited.
45.4(2)°, and the aryl ring bonded to palladium in 10
forms an angle of 36.2(1)° with the coordination plane.
The six-membered ring conformations in 5 and 10 are
quasi-boats, Pd and CH2 at the prows, the two rings in
each complex being related by a putative 2-axis through
PdꢀC(0), this symmetry and conformation carrying
through rather less exactly to the counterpart arrays of
6 and 8 where overt or covert disorder is prevalent.
3. Conclusions
In each of the four crystalline arrays, one formula
unit devoid of crystallographic symmetry comprises the
asymmetric unit of the structure, the arrays for 5 and 6
being neutral molecular complexes, unsolvated, and for
8 and 10 ionic complexes incorporating solvent in the
coordination sphere of the metal, rather than the
poorly coordinating anion. Not surprisingly, the quasi-
spherical anions in 8 and 10 are disordered. Disorder is
resolved for the hydrocarbon string of the ligand in 6,
while the large displacement amplitudes therein in 7,
may be presumed to indicate unresolved disorder. Asso-
ciated geometries for these systems should be treated
with caution.
Organopalladium(II) complexes containing symmet-
rical [NꢀC(sp3)ꢀN]− intramolecular coordination sys-
tems with six-membered pallada(II)cyclic rings are
readily formed on C(sp3)ꢀH activation of simple
reagents (XCH2CH2)2CH for a range of heterocyclic
groups X=pyridin-2-yl, pyrazol-1-yl, N-methylimida-
zol-2-yl. The organic reagents are readily accessed via
reactions of alkali metal reagents with dibromoalkanes,
and thus offer interesting routes to studies in cy-
clometallation chemistry involving alkyl CꢀH
activation.
The complexes have square planar geometry for pal-
4. Experimental
ladium (Table 2, Figs.
2
and 3). For both
[NꢀC(sp3)ꢀN]− and [NꢀC(sp2)ꢀN]− units, CꢀPdꢀN an-
gles at palladium are close to 90°. These angles are
within ca. 1° of 90° for the [NꢀC(sp2)ꢀN]− complex 10
and the reported complex PdCl{3,5-Me2-2,6-
(pzCH2)2C6H-N,C,N%} [6], and within ca. 3° of 90° for
the [NꢀC(sp3)ꢀN]− pyrazole donor system in 8; the
2-Picolyllithium [18] was prepared as described [17].
Solvents were dried and distilled, stored under nitrogen
and freshly distilled immediately before use, and all
procedures were carried out under nitrogen.
NMR spectra were recorded with either a Varian
Unity Inova 400 WB spectrometer operating at 100.587
(13C), 399.716 (1H) MHz, or a Varian Gemini 200
spectrometer operating at 50.29 (13C), 199.975 (1H)
MHz, at room temperature unless otherwise indicated.
Chemical shifts are given in parts per million relative to
SiMe4.
related
platinum(II)
complex
PtBr{2,6-(3,5-
Me2pzCH2)2C6H3-N,C,N%} has CꢀPtꢀN angles of
85.4(4) and 88.6(4)° [11].
The PdꢀO(2) distance in the acetone complex 8,
,
2.263(6) A, longer than in the cyclopalladated azoben-
zene complex Pd(C6H4NꢁNPh-C,N)(PPh3)(OCMe2),
Microanalyses were determined by the Central Sci-
ence Laboratory, University of Tasmania.
2.141(5) [12], and the PdꢀO distance in the aqua com-
,
plex 10, 2.200(3) A, is similar to that in other
organopalladium(II) complexes containing the aqua lig-
4.1. Synthesis of reagents
3
2
,
and trans to an sp carbon, 2.124(2) A [13], or an sp
,
carbon, 2.20(1) [14] and 2.132(3) A [15], but longer than
in an organopalladium(IV) complex where the aqua
ligand is opposite a pyrazole donor which has a weaker
4.1.1. 1,5-Bis(pyridin-2-yl)pentane (1)
To a stirred solution of 2-picolyllithium (30 mmol, 1
M solution in diethyl ether) was added, dropwise over
1 h, a solution of 1,3-dibromopropane (10 mmol) in
diethyl ether (20 ml). The mixture was stirred for 3 h,
then hydrolysed by the dropwise addition of water (50
ml). The aqueous layer was separated and extracted
with dichloromethane (3×20 ml), and the organic frac-
tion dried over MgSO4, filtered, and evaporated to
dryness in a vacuum. The product was purified by
bulb-to-bulb distillation (1.45 g, 64%). B.p.: (140°C,
,
trans influence than an alkyl or aryl group, 2.035(4) A
[16].
For the coordination mean planes, the donor atoms
,
are within 0.32(1) A of the mean planes for 5, 6 and 10
,
and the palladium atoms are within 0.070(3) A for these
complexes; the acetone complex (8) exhibits larger devi-
,
ations [−0.08(1)–0.29(2) A] for the donor atoms and
,
0.075(3) A for the palladium atom (Table 2). The mean
1
planes of nitrogen donor rings form dihedral angles
with the coordination plane ranging from 14.2(4)–
0.08 Torr). H-NMR (CDCl3, 200 MHz): l 8.50 (dd,
3J=4.9, 5J=1.8 Hz, 2, H6), 7.58 (m, 2, H4), 7.12–7.04

198
A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
Table 2
Selected molecular geometries for Pd{CH(CH2CH2py)2-N,C,N%}Cl (5), Pd{CH(CH2CH2pz)2-N,C,N%}Cl (6), [Pd{CH(CH2CH2pz)2-
N,C,N%}(OCMe2)][BF4] (8), and [Pd{2,6-(pzCH2)2C6H3-N,C,N%}(OH2)][BF4] (10) a
5
6
8
10
,
Distances (A)
PdꢀX
2.457(2)
2.050(8)
2.058(4)
2.060(5)
2.463(2)
1.99(1), 2.086(9)
2.032(4)
2.263(6)
2.01(1)
2.045(8)
2.027(9)
2.200(3)
1.973(4)
2.008(3)
2.021(3)
PdꢀC(0)
PdꢀN(11)
PdꢀN(21)
2.032(4)
Angles (°)
XꢀPdꢀC(0)
175.0(3)
90.9(1)
92.5(1)
85.6(3)
90.9(3)
176.3(2)
122.2(4)
118.6(4)
121.4(4)
119.9(4)
113.9(5)
119.0(5)
–
173.8(4), 169.1(3)
91.7(1)
88.9(1)
85.6(4), 93.6(3)
94.1(4), 85.5(3)
177.9(2)
126.5(3)
128.1(4)
123.0(3)
130.2(4)
173.4(4)
91.8(1)
85.1(3)
92.5(5)
91.4(5)
171.1(3)
127.6(7)
126.1(6)
128.5(7)
126.6(8)
116(1)
177.7(1)
88.3(1)
92.7(1)
89.7(1)
89.3(1)
178.6(1)
122.6(2)
131.5(3)
121.7(3)
131.6(3)
120.1(3)
120.5(3)
–
XꢀPdꢀN(11)
XꢀPdꢀN(21)
C(0)ꢀPdꢀN(11)
C(0)ꢀPdꢀN(21)
N(11)ꢀPdꢀN(21)
PdꢀN(11)ꢀC/N(12)
PdꢀN(11)ꢀC(15/16)
PdꢀN(21)ꢀC/N(22)
PdꢀN(21)ꢀC(25/26)
PdꢀC(0)ꢀC(122)
PdꢀC(0)ꢀC(222)
PdꢀO(2)ꢀC(2)
118.2(8), 112.9(6)
118.4(8), 114.3(6)
–
116(1)
124.9(5)
2
,
Plane parameters ( , atom de6iations lA)
2(X,C(0), N(11,21))(1)
34
0.038(2)
9
0.009(8)
18
0.054(8)
227, 372
0.015(3), 0.070(3)
0.9
0.137(10)
1.3
361*
0.075(3)
0.8
0.36(2)
0.2
0.14(2)
82
0.002(1)
2.4
0.070(7)
14
0.206(7)
lPd
2(N(11)ꢀC(15/16))(2)
lPd
2(N(21)ꢀC(15/16))(3)
lPd
0.295(9)
Other atom de6iations from the X, C(0) N(11,21) plane:
lPd
0.038(2)
0.797(9)
−0.844(8)
−0.739(8)
0.728(8)
1.697(9)
0.959(9)
−1.468(9)
−0.524(9)
−0.06(1)
−0.002(2)
0.012(6)
−0.015(3), −0.070(3)
0.507(8), 0.426(8)
−0.321(9), −0.353(9)
−0.497(8), −0.575(8)
0.679(8), 0.645(7)
0.60(2)/1.28(1), 0.48(2)/1.17(1)
0.58(1), 0.46(1)
−1.315(10), −1.418(10)
−0.59(1), −0.71(1)
−0.22(1), 0.31(2)
−0.075(3)
0.29(2)
0.022(1)
−0.24(2)
0.64(2)
0.001(1)
0.640(5)
−0.572(6)
−0.638(6)
0.737(6)
1.460(6)
0.670(6)
−1.504(6)
−0.738(6)
−0.027(5)
−0.017(4)
0.017(4)
lN/C(12)
lC(15/16)
lN/C(22)
lC(25/26)
lC(121)
lC(122)
lC(221)
lC(222)
lC(0’,0)
lX
0.17(2)
−0.21(3)
−0.75(3)
−0.62(3)
−0.29(2)
0.037(7)
0.07(1)
−0.003(2), 0.005(2)
0.022(6), −0.034(6)
0.019(6), −0.035(6)
lN(11)
lN(21’)
0.011(6)
0.08(1)
0.018(4)
Interplanar dihedral angles (°)
(1)/(2)
(1)/(3)
(2)/(3)
45.4(2)
40.2(2)
85.6(2)
23.6(2), 22.2(2)
34.3(2), 35.6(2)
57.8(3)
14.2(4)
26.2(5)
34.1(6)
34.3(1)
40.2(2)
73.8(2)
Torsion angles (°)
C(0)ꢀPdꢀN(11)ꢀC/N(12)
C(0)ꢀPdꢀN(21)ꢀC/N(22)
PdꢀN(11)ꢀC/N(12)ꢀC(121)
PdꢀN(21)ꢀC/N(22)ꢀC(221)
N(11)ꢀC/N(12)ꢀC(121)ꢀC(222)
N(21)ꢀC/N(22)ꢀC(221)ꢀC(222)
C/N(12)ꢀC(121)ꢀC(122)ꢀC(0)
C/N(22)ꢀC(221)ꢀC(222)ꢀC(0)
C(121)ꢀC(122)ꢀC(0)ꢀPd
C(221)ꢀC(222)ꢀC(0)ꢀPd
C(121)ꢀC(122)ꢀC(0)ꢀC(222)
C(221)ꢀC(222)ꢀC(0)ꢀC(122)
N(11)ꢀPdꢀC(0)ꢀC(122)
−46.9(5)
−37.7(5)
−0.4(7)
5.0(7)
58.6(7)
55.9(7)
−49.6(8)
−74.1(7)
−14.7(9)
26.7(9)
−164.3(6)
174.7(6)
51.1(6)
−159.2(7)
−130.2(6)
19.5(7)
−31.8(6)
−21.8(6)
25(1), −10(1)
−12(7)
−20(2), 54(1)
60.3(7)
36(2), −41
−67(1), −40(1)
(?)
25(1), −20(1)
(?)
175(1), −156.9(8)
41.6(9), 5.9(8)
−168.4(1), −132.8(7)
−136.3(9), −172.2(8)
13.7(9), 49.1(7)
−15.3(8)
15.7(10)
15(1)
1(2)
0(2)
−33.6(3)
−34.3(3)
−7.1(5)
−7.6(5)
56.1(5)
18(3)
57.8(5)
−16(4)
−16(4)
11(4)
−6(3)
−175(3)
180(3)
4(2)
−171(1)
−168(2)
17(1)
−53.1(5)
−54.3(5)
0.4(5)
−0.1(5)
−179.7(3)
180.0(4)
35.5(3)
−144.4(3)
−143.5(3)
36.6(3)
N(11)ꢀPdꢀC(0)ꢀC(222)
N(21)ꢀPdꢀC(0)ꢀC(122)
N(21)ꢀPdꢀC(0)ꢀC(222)
2
a For the acetone skeleton,  is 2,4, lPd 0.59(2) A, and the dihedral to N2CO 74.6(4)°. The distance between the C(0,0%) components in 6 is
,
,
0.62(2) A; where two entries are given, these are for the two disordered arrays; certain of the torsion angles are determined by more than one
component and, having some ambiguity, are denoted (?). In 10 the dihedral angles for the coordinated C6 ring to the planes 1–3 are 36.2(1), 49.8(2)
and 56.6(2)°.

A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
199
3
(m, 4, H3,5), 2.77 (t, J=7.8 Hz, 4, py CH2), 1.77 (m,
4, pyCH2CH2), 1.42 (m, 2, pyCH2CH2CH2). 13C{1H}-
NMR (CDCl3, 50 MHz): l 162.8 (C6), 149.7 (C2),
136.7 (C4), 123.2 (C3), 121.4 (C5), 38.8 (pyCH2), 30.2
(pyCH2CH2), 29.6 (pyCH2CH2CH2). Anal. Calc. for
C15H20N2: C, 79.61; H, 8.01; N, 12.38. Found: C, 79.59;
H, 8.24; N, 12.24%.
4.1.2. 1,5-Bis(pyrazol-1-yl)pentane (2)
To a stirred suspension of finely cut potassium (0.94
g, 24 mmol) in tetrahydrofuran (30 ml) was added
pyrazole (1.70 g, 25 mmol). The mixture was heated to
reflux and maintained at this temperature until beads of
molten potassium were no longer evident (ꢀ90 min).
The solution was cooled and 1,5-dibromopentane (10
mmol) added. The solution was refluxed for 8 h, then
filtered and the solvent removed in a vacuum leaving a
pale yellow oil. The product was purified by bulb-to-
bulb distillation (135°C, 0.1 Torr). Yield: 79%. 1H-
3
NMR (CDCl3, 200 MHz): l 7.45 (d, J=1.80 Hz, 2,
H3), 7.29 (d, 3J=2.28 Hz, 2, H5), 6.18 (‘t’, 2, H4), 4.06
3
3
(t, J=7.01 Hz, 4, pzCH2), 1.84 (q, J=7.40 Hz, 4,
pzCH2CH2), 1.22 (m, 2, pzCH2CH2CH2). 13C{1H}-
NMR (CDCl3, 50 MHz): l 139.6 (C3), 129.4 (C5),
105.7 (C4), 52.2 (pzCH2), 30.4 (pzCH2CH2), 24.1
(pzCH2CH2CH2). Anal. Calc. for C11H16N4: C, 64.68;
H, 7.90; N, 27.43. Found: C, 64.51; H, 7.98; N, 27.48%.
Fig. 2. Projection of (a)
a molecule of Pd{CH(CH2CH2py)2-
N,C,N%}Cl (5), and (b) a molecule of Pd{CH(CH2CH2pz)2-N,C,N%}Cl
(6) illustrating disorder in the latter complex. The projections show
20% thermal ellipsoids for the non-hydrogen atoms, hydrogen atoms
,
having an arbitrary radius of 0.1 A.
4.1.3. 1,5-Bis(N-methylimidazol-2-yl)pentane (3)
To a stirred suspension of N-methylimidazole (3.16 g,
38.5 mmol) in diethyl ether (20 ml) at −70°C was
added n-butyllithium (16.1 ml of 2.4 M, 38.5 mmol).
The mixture was allowed to warm to −10°C and
maintained at this temperature for 30 min. The mixture
(a white suspension) was cooled to −70°C and 1,5-di-
bromopentane (2.5 ml, 18.4 mmol) was added. The
solution was allowed to warm to ambient temperature
and stirred for 2 h. The reaction mixture was hydrolysed
with water (2 ml) and the solvent removed in a vacuum.
The product was extracted with dichloromethane (3×
20 ml) and the combined organic extracts washed with
water (3×20 ml), followed by bulb-to-bulb distillation
(145°C, 0.2 Torr) to give a pale yellow oil (1.28 g, 30%
but variable 5–30%). 1H-NMR (CDCl3, 200 MHz):
3
3
l 6.87 (d, J=1.28 Hz, 2, H4 or H5), 6.75 (d, J=
1.26 Hz, 2, H4 or H5), 3.52 (s, 6, NꢀCH3), 4.06 (t,
3J=5.14 Hz, 4, mimCH2), 1.78 (q, 3J=7.68 Hz, 4,
mimCH2CH2), 1.50 (m, 2, mimCH2CH2CH2). 13C{1H}-
NMR (CDCl3, 50 MHz): l 148.9 (C1), 127.4 (C4),
120.8 (C3), 33.0 (NꢀCH3), 29.6 (mimCH2CH2), 27.9
(mimCH2CH2), 27.1 (mimCH2CH2CH2). Anal. Calc.
for C13H20N4: C, 67.21; H, 8.68; N, 24.12. Found: C,
67.20; H, 8.86; N, 24.21%.
Fig. 3. Projection of the cation in (a) [Pd{CH(CH2CH2pz)2-
N,C,N%}(OCMe2)][BF4] (8), and (b) [Pd{2,6-(pzCH2)C6H3-
N,C,N%}(OH2)][BF4] (10). The projections show 20% thermal
ellipsoids for the non-hydrogen atoms, hydrogen atoms having an
4.1.4. 1,3-Bis(pyrazol-1-ylmethyl)benzene (4)
This previously reported compound [5] was made by
a modified procedure. Pyrazole (1.13 g, 16.6 mmol) was
,
arbitrary radius of 0.1 A.

200
A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
added to a stirred suspension of finely cut potassium
(0.62 g, 15.9 mmol) in tetrahydrofuran (40 ml) under an
argon atmosphere. The mixture was heated to reflux
and maintained at this temperature until beads of
molten potassium were no longer evident (ꢀ1 h). The
resultant white suspension was cooled to ambient tem-
perature and 1,3-bis(bromomethyl)benzene (2.00 g, 7.6
mmol) added in one portion. The reaction mixture was
refluxed overnight, then quenched by addition of water
(0.1 ml), filtered and the solvent removed in a vacuum.
The product was purified by bulb-to-bulb distillation to
give a clear oil that formed as a white solid (165°C, 0.2
h. The solvent was removed in a vacuum at 50°C
leaving a yellow oil. The oil was dissolved in acetone (5
ml) and lithium chloride (0.1 g) was added to the
solution, which was stirred overnight. The solvent was
stripped on a rotary evaporator and the product ex-
tracted with dichloromethane (3×2 ml). The solution
was filtered through Celite and the solvent removed in
a vacuum. The resultant yellow oil was dissolved in
acetone (1 ml) and cooled to −20°C for 4 h. After this
time the product had crystallised, the solution was
decanted and the product washed with petroleum ether
(b.p. 60–80°C) (3×2 ml). The product was recrys-
tallised from CH2Cl2–petroleum ether (b.p. 60–80°C)
and finally dried in a vacuum to give a pale yellow solid
(0.054 g, 35%). Crystals suitable for single crystal X-ray
structure determination were grown from a CH2Cl2–
petroleum ether (b.p. 60–80°C) solution. 1H-NMR
1
Torr), (1.59 g, 88%). H-NMR (CDCl3, 200 MHz): l
3
3
7.55 (d, J=1.8 Hz, 2, H3-pz), 7.38 (d, J=2.3 Hz, 2,
3
3
H5-pz), 7.29 (t, J=7.7 Hz, 2, H5), 7.12 (d, J=7.8
Hz, 2, H4, H6), 7.06 (s, 1, H2), 6.28 (‘t’, 2, H4-pz),
5.31 (s, 4, C6H4(CH2)2). 13C{1H}-NMR (CDCl3, 50
MHz): l 139.6, 137.3, 129.3, 129.3, 127.1, 126.6, 106.0,
55.5.
3
(CDCl3, 200 MHz) l 8.41 (d, J=2.36 Hz, 2, H3), 7.42
3
(d, J=2.57 Hz, 2, H5), 6.26 (‘t’, 2, H4), 4.53–4.40 (m,
2, pzCH2), 4.22–4.10 (m, 2, pzCH2), 2.54 (m, 1,
pzCH2CH2CH), 1.73–1.56 (m, 2, pzCH2CH2), 1.49–
1.31 (m, 2, pzCH2CH2). 13C-NMR (CDCl3, 50 MHz) l
144.9 (C3), 131.6 (C5), 106.6 (C4), 52.0 (pzCH2), 34.4
(pzCH2CH2), 28.4 (pzCH2CH2CH). Anal. Calc. for
C11H15ClN4Pd: C, 38.28; H, 4.38; N, 16.23. Found: C,
38.58; H, 4.34; N, 16.01%.
4.2. Synthesis of complexes
4.2.1. Pd{CH(CH2CH2py)2-N,C,N%}Cl (5)
A solution of palladium(II) acetate (0.20 g, 0.89
mmol) and 1,5-bis(pyridin-2-yl)pentane (0.24 g, 1.05
mmol) in glacial acetic acid (3 ml) was stirred at 110°C
for 3 h. The solvent was removed in a vacuum at 50°C
to give a yellow oil. The oil was dissolved in acetone (5
ml), lithium chloride (0.4 g) was added and the solution
stirred for 15 h. The solvent was removed in a vacuum,
the residue was extracted with dichloromethane (20 ml),
and the solution filtered through Celite and the solvent
removed in a vacuum. The resulting yellow oil was
dissolved in dichloromethane (1 ml) and impurities
precipitated by addition of petroleum ether (5 ml, b.p.
60–80°C). The solution was decanted and the solvent
removed in a vacuum. The resulting yellow oil was
dissolved in acetonitrile (0.4 ml), from which the
product precipitated as a yellow powder (0.04 g, 12%).
Crystals suitable for single-crystal X-ray structure de-
termination were grown from a CHCl3–petroleum
4.2.3. Pd{CH(CH2CH2mim)2-N,C,N%}Cl (7)
A solution of palladium(II) acetate (0.79 g, 3.5
mmol) and 1,5-bis(N-methylimidazol-2-yl)pentane (0.91
g, 3.9 mmol) in acetic acid (40 ml) was stirred at 110°C
for 5 h. The solvent was removed in a vacuum at 50°C
leaving a brown oil. The oil was dissolved in acetone
(100 ml) and lithium chloride (1 g) in water (10 ml) was
added to the solution, which was stirred overnight. The
solvent was stripped on a rotary evaporator and the
product extracted with dichloromethane (3×50 ml).
The combined organic extracts were washed with water
(3×100 ml) and then dried over MgSO4. The solution
was filtered and the solvent removed in a vacuum to
1
give a tan solid (0.22 g, 17%). H-NMR (CDCl3, 400
1
3
3
ether (b.p. 60–80°C) solution. H-NMR (CDCl3, 400
MHz): l 8.02 (d, J=1.66 Hz, 2, H4), 6.70 (d, J=
1.64 Hz, 2, H5), 3.55 (s, 6, NꢀCH3), 2.93–2.82 (m, 2,
mimCH2), 2.68–2.60 (m, 2, mimCH2), 2.25 (m, 1,
MHz): l 9.41 (dd, 3J=5.7 Hz, 5J=1.8 Hz, 2, H6), 7.68
(m, 2, H4), 7.26 (m, 2, H3), 7.15 (m, 2, H5), 3.45–3.30
(m, 2, pyCH2), 3.02–2.90 (m, 2, pyCH2), 2.56 (m, 1,
pyCH2CH2CH), 1.35–1.05 (m, 4, pyCH2CH2).
13C{1H}-NMR (CDCl3, 100 MHz): l 162.1 (C6), 155
(C2), 138.2 (C4), 124.4 (C3), 121.7 (C5), 40.0 (pyCH2),
37.0 (pyCH2CH2CH), 32.9 (pyCH2CH2). Anal. Calc.
for C15H17N2Pd: C, 49.07; H, 4.67; N, 7.63. Found: C,
48.96; H, 4.72; N, 7.72%.
mimCH2CH2CH), 1.87–1.70 (m,
2 mimCH2CH2),
1.15–1.05 (m, 2, mimCH2CH2. 13C{1H}-NMR (CDCl3,
50 MHz): l 148.76 (C2), 130.97 (C4), 119.65 (C5),
33.47 (NꢀCH3), 32.95 (mimCH2), 32.78 (mimCH2CH2-
CH), 25.55 (mimCH2CH2).
4.2.4. [Pd{CH(CH2CH2pz)2-N,C,N%}(OCMe2)][BF4] (8)
To a suspension of 6 (0.050 g, 0.15 mmol) in acetone
(1 ml) was added a solution of AgBF4 (0.028 g, 0.15
mmol) in acetone (1 ml) and the mixture was stirred
overnight. The solution was filtered through Celite and
the solvent reduced to a minimum in a vacuum. Yellow
4.2.2. Pd{CH(CH2CH2pz)2-N,C,N%}Cl (6)
A solution of palladium(II) acetate (0.10 g, 0.45
mmol) and 1,5-bis(pyrazol-1-yl)pentane (0.10 g, 0.49
mmol) in acetic acid (5 ml) was stirred at 100°C for 20

A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
201
1
crystals formed on standing which were collected by
decanting the remaining solution, and then dried in a
vacuum to give yellow crystals (0.023 g, 34%). Crystals
suitable for single-crystal X-ray structure determination
ethyl ether. H-NMR (acetone-d6, 200 MHz): l 8.20 (d,
3J=2.5 Hz, 2, H3-pz), 7.79 (d, J=1.8 Hz, 2, H5-pz),
3
7.19–7.03 (m, 3, C6H3(CH2)2), 6.49 (‘t’, 2, H4-pz), 5.61
(s, 4, C6H3(CH2)2). 13C{1H}-NMR (acetone-d6, 50
MHz): l 143.1, 137.5, 134.4, 128.0, 126.8, 108.3, 58.6.
Anal. Calc. for C14H15BF4N4PdO: C, 37.49; H, 3.37; N,
12.49. Found: C, 37.71; H, 3.37; N, 12.39%.
1
were grown from an acetone solution. H-NMR (ace-
tone-d6, 200 MHz): l 8.01 (d, 3J=2.43 Hz, 2, H5), 7.52
3
(d, J=2.14 Hz, 2, H3), 6.46 (‘t’, 2, H4), 4.79–4.66 (m,
2, pzCH2), 4.44–4.31 (m, 2, pzCH2), 2.97 (m, 1,
pzCH2CH2CH), 1.85–1.65 (m, 2, pzCH2CH2), 1.35–
1.19 (m, 2, pzCH2CH2). 13C{1H}-NMR (acetone-d6, 50
MHz): l 42.5 (C3), 134.6 (C5), 108.1 (C4), 52.5
(pzCH2), 34.8 (pzCH2CH2), 32.6 (pzCH2CH2CH).
Anal. Calc. for C14H21BF4N4OPd: C, 36.99; H, 4.66; N,
12.33. Found: C, 36.79; H, 4.60; N, 12.49%.
4.2.7. Thermogra6imetric analysis
The complex PdCl2{1,5-(pzCH2)2C6H4} (0.01209 g,
0.029 mmol) was placed in an aluminium oxide TGA
crucible, and under an argon gas flow the sample was
heated from 150–300°C at a rate of 2° min−1 (Setaram
TGA 92). The sample lost 0.01210 g in the range
180–280°C, a loss of 10.0% (Calc. for loss of HCl
8.8%). On cooling the sample was dissolved in CDCl3
to give a 1H-NMR spectrum identical to that of
PdCl{2,6-(pzCH2)2C6H3} (9).
4.2.5. PdCl{2,6-(pzCH2)2C6H3} (9)
A solution of PdCl2(1,5-cyclooctadiene) (0.10 g, 0.35
mmol) and 1,3-bis(pyrazol-1-ylmethyl)benzene (4)
(0.084 g, 0.35 mmol) in acetonitrile (15 ml) was stirred
overnight. The solution was decanted and the insoluble
product was washed with acetonitrile (5 ml), acetone (5
ml) and petroleum ether (40–60°) (5 ml). The resultant
orange–yellow product, PdCl2{1,3-(pzCH2)2C6H3}, was
dried in a vacuum (0.113 g, 77%). This complex was
insoluble in standard NMR solvents. Anal. Calc. for
C14H14Cl2N4Pd, C: 40.46; H: 3.40; N: 13.48. Found, C:
40.41; H: 3.42; N: 13.61%. The complex (0.125 g, 0.30
mmol) was placed in a flask on a bulb-to-bulb distilla-
tion apparatus. The flask was evacuated and heated
with rotation to 230°C and maintained at this tempera-
ture until the solid changed colour from orange/yellow
to grey. The product was extracted with CH2Cl2 (50 ml)
and filtered through Celite. The solvent was reduced in
a vacuum to ꢀ2 ml and the product precipitated by
the addition of diethyl ether (20 ml). The product was
collected by filtration and dried in a vacuum leaving a
4.3. X-ray data collection, structure determination and
refinement for complexes 5, 6, 8 and 10
Room temperature single counter/four-circle diffrac-
tometer data sets were measured to the specified redun-
dancy within the specified 2qmax limit (2q/q scan mode;
,
monochromatic MoꢀKa radiation, u=0.71073 A; T ca.
295 K) yielding Nt total reflections, these being merged
to Nr unique (Rint quoted), No with I\3|(I) being
considered ‘observed’ and used in the full-matrix least-
squares refinements, Gaussian absorption corrections
being applied. Anisotropic thermal parameters were
refined for the non-hydrogen atoms (x, y, z, Uiso)H
being included constrained at estimated values. Con-
ventional residuals R, Rw on ꢀFꢀ are quoted at conver-
gence, statistical weights derivative of |2(I)=|2(Idiff)+
0.0004|4(Idiff) being applied. Neutral atom complex
scattering factors were employed, computation using
the XTAL 3.4 program system [18].
1
white powder (0.060 g, 53%). H-NMR (CDCl3, 200
MHz): l 8.17 (d, 3J=2.2 Hz, 2, H3-pz), 7.61 (d,
3J=2.8 Hz, 2, H5-pz), 7.06 (s, 3, C6H3(CH2)2), 6.33
(‘t’, 2, H4-pz), 5.34 (sb, 4, C6H3(CH2)2). 13C{1H}-NMR
(CDCl3, 50 MHz): l 144.5, 136.4, 131.5, 126.7, 125.3,
107.1, 58.9. Anal. Calc. for C14H13ClN4Pd: C, 44.35; H,
3.46; N, 14.78. Found: C, 44.30; H, 3.33; N, 14.27%.
For complex 5 Nt (sphere)=13 086, Rint=0.11.
For complex 6, conformational disorder, most pro-
nounced in the aliphatic component of segment 1 of the
ligand was modelled in terms of individual pairs of
atom components for C(0, 121), with site occupancies
set at 0.5 after trial refinement. Unique data.
The crystal of complex 8 (capillary mounted) decom-
posed by ca. 70% during data collection, appropriate
scaling being applied. The anion was modelled as disor-
dered over two sets of sites, occupancies set at x=
0.85(2), 1−x after preliminary refinement. The
coordinated ligand was modelled as acetone on the
basis of geometry and refinement behaviour. Large
displacement amplitudes in the hydrocarbon string are
presumed to indicate unresolved disorder. Nt (hemi-
sphere)=6476, Rint=0.045.
4.2.6. [Pd(OH2){2,6-(pzCH2)2C6H3}][BF4] (10)
A solution of AgBF4 (0.055 g, 0.29 mmol) in water
(3.0 ml) was added to a stirred suspension of PdCl{2,6-
(pzCH2)2C6H3} (9) (0.108 g, 0.29 mmol) in acetone (40
ml). The solution was stirred in the absence of light for
10 min. The solution was filtered and the solvent re-
moved in a vacuum. The residue was extracted with
acetone (3 ml) and the product crystallised as yellow
crystals on addition of diethyl ether (0.087 g, 67%).
Crystals suitable for single-crystal X-ray structure de-
termination were grown from a solution of acetone–di-
In 10, similar anion disorder was resolved and
refined, x being 0.73(1), for F(2–4), rotationally disor-

202
A.J. Canty et al. / Journal of Organometallic Chemistry 607 (2000) 194–202
[2] A.L. Seligson, W.C. Trogler, Organometallics 12 (1993) 738.
[3] K. Hiraki, Y. Fuchita, Y. Matsumoto, Chem. Lett. 11 (1984)
1947.
dered about BꢀF(1). Nt (hemisphere)=7844, Rint
0.017.
=
[4] M. Ohff, A. Ohff, M.E. van der Boom, D. Milstein, J. Am.
Chem. Soc. 119 (1997) 11687.
[5] A.J. Canty, R.T. Honeyman, J. Organomet. Chem. 387 (1990)
247.
5. Supplementary material
[6] C.M. Hartshorn, P.J. Steel, Organometallics 17 (1998) 3487.
[7] M. Nonoyama, Polyhedron 4 (1985) 765.
[8] A.J. Canty, N.J. Minchin, B.W. Skelton, A.H. White, J. Chem.
Soc. Dalton Trans. (1987) 1477.
[9] A.J. Canty, C.V. Lee, Organometallics 1 (1982) 1063.
[10] B. Brzezinski, G. Zundel, Chem. Phys. Lett. 70 (1980) 55.
[11] A.J. Canty, J. Patel, B.W. Skelton, A.H. White, J. Organomet.
Chem. 599 (2000) 195.
Crystallographic data has been deposited with the
Cambridge Crystallographic Data Centre (deposition
nos.: 147416–147419). Copies of this information may
be obtained free of charge from: The Director, CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK (Fax:
+44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or
www: http://www.ccdc.cam.ac.uk).
[12] J. Vicente, A. Arcas, D. Bautista, A. Tiripicchio, M.T.
Camellini, New J. Chem. 20 (1996) 345.
[13] F. Maassarani, M. Pfeffer, G. Le Borgne, Organometallics 6
(1987) 2043.
[14] A.J. Deeming, I.P. Rothwell, M.B. Hursthouse, L. New, J.
Chem. Soc. Dalton Trans. (1978) 1490.
Acknowledgements
We thank the Australian Research Council for finan-
cial support.
[15] P. Castan, J. Jaud, S. Wimmer, F.L. Wimmer, J. Chem. Soc.
Dalton Trans. (1991) 1155.
[16] A.J. Canty, H. Jin, A.S. Roberts, B.W. Skelton, A.H. White,
Organometallics 15 (1996) 5713.
[17] R.B. Woodward, E.C. Kornfeld, Organic Syntheses, Collective
vol. III (1955) 413.
References
[18] S.R. Hall, G.S.D. King, J.M. Stewart (Eds.), The XTAL 3.4
User’s Manual, University of Western Australia, Lamb, Perth,
1995.
[1] N.A. Al-Salem, H.D. Empsall, R. Markham, B.L. Shaw, B.
Weeks, J. Chem. Soc. Dalton Trans. (1979) 1972.
.